Improving the accuracy of surface plasmon resonance angle determination by apodizing the transmission function of an acousto-optical tunable filter

Subject of study. The influence of sidelobes relative to the central band of the transmission spectrum of an acousto-optical tunable filter on the accuracy of surface plasmon resonance (SPR) angle determination compared with the case of monochromatic radiation is investigated. Aim of study. The aim of this study is to improve the accuracy of the SPR method when broadband optical radiation is passed through an acousto-optical tunable filter by reducing the systematic error in determining the resonance angle relative to the case of monochromatic radiation. Method. An apodization technique is proposed to suppress the influence of secondary maxima in the transmission function of the acousto-optical tunable filter, whose shape is close to the squared cardinal sine function, by tuning the central wavelength and applying mathematical postprocessing. Main results. The systematic error in determining the resonance angle in the SPR technique is reduced by a factor of 1.5. Practical significance. Reducing the measurement error of the resonance angle in the SPR method will allow the determination of the optical constants of dielectric coatings with high accuracy and the analysis of their depth distribution within a thin layer. Achieving high accuracy and resolution will enable nondestructive investigations of subwavelength-scale processes in the visible and infrared ranges, such as diffusion and adhesion of thin films of metals and dielectrics, which is important for applied problems in nanotechnology and materials science, as well as for sensor applications in biomedicine.